Device for recording measurement data

ABSTRACT

The device is used to record measurement data and has a housing, a housing interior and a membrane that is held by the housing and delimits the housing interior in regions. At least one sensor is arranged inside the housing interior. Furthermore, a thermocatalytic element for the decomposition of at least one gas is arranged in the housing interior.

BACKGROUND OF THE INVENTION

The invention concerns a device for acquiring measurement data, whichhas a housing, an inner chamber of the housing, and a membrane that issupported by the housing and bounds part of the inner chamber of thehousing, and in which at least one sensor is installed within the innerchamber of the housing.

Devices of this type use measurement technology, for example, todetermine gases that pass through the membrane. In this regard, first,the membrane shields the sensor from the environment, and, second, themembrane ensures that only predefined gases are able to enter the areaof the sensor in appreciable concentrations. Sensor systems of this typeare described, for example, in EP 0 823 055 B1 and EP 1 114 297 B1.

One problem with the use of sensors and measurement systems of this typeis that the gases that pass through the membrane to enter theenvironment of the sensor escape back out of the area of the sensor atonly a relatively slow rate when the gas concentration in the vicinityof the measurement system changes. When the gases to be detected arepresent in concentrations that vary as a function of time, this givesrise to significant time constants, which result in measuringsluggishness of the overall system.

Therefore, in the case of movement through a local measurement area withdifferent concentrations to be measured or with concentrations to bemeasured that vary as a function of time, the previously knownmeasurement systems are still not able to meet all of the requirementsthat are placed on optimum measurement quality.

SUMMARY OF THE INVENTION

Therefore, the objective of the present invention is to improve a deviceof the type described above in such a way that improved measurementdynamics are obtained.

In accordance with the invention, this objective is achieved byinstalling a thermocatalytic element in the inner chamber of the housingto decompose at least one gaseous hydrocarbon and by designing the innerchamber of the housing in a way that supports gas circulation.

By installing a thermocatalytic element in the inner chamber of thehousing, it is possible significantly to minimize interfering gasconcentrations within a short period of time. These may be gases thatpass through the membrane along with the gas to be measured and wouldotherwise distort the measurement result. In particular, however, thegas to be measured can be thermocatalytically decomposed to support ahighly dynamic measurement with only slight time-lag effects. Especiallythermocatalytic sensors, so-called pellistors, can be used as thethermocatalytic elements.

The measurement system of the invention is suitable, for example, fordetecting leaks in offshore pipelines. Due to its very rapid responsetime, it can also be used in submersible vehicles. Since its long-termstability is very high, the measurement system of the invention is alsosuitable for long-term applications over periods of a year or more. Whenoptical sensors are used, long-term stability of up to ten years isachieved.

Gas circulation can be actively generated by impellers or can beproduced as a secondary effect of the thermocatalytic decomposition. Thethermocatalytic decomposition usually leads to local gas heating, whichcauses movement of the gases enclosed in the inner chamber of thehousing. Local gas flow or gas turbulence can be generated especially bya suitable design of the walls of the inner chamber of the housing, andthis promotes contact of the hydrocarbons that penetrate the innerchamber of the housing through the membrane with the thermocatalyticsensor.

Use of the measurement system of the invention in the petroleum industryis possible if the thermocatalytic element is designed for thedecomposition of at least one hydrocarbon.

Offshore applications are made possible by designing the housing for usein water.

Pipeline leak detection is promoted by designing the measurement systemfor underwater gas detection.

Extremely high measurement accuracy can be realized by designing thesensor as an optical sensor.

To promote low energy consumption, it is proposed that the sensor bedesigned as a semiconductor sensor.

It is advantageous to design the membrane to be gas-permeable.

Simple realization of the membrane from the standpoint of productionengineering is promoted by forming the membrane as a coating.

Arrangement of the membrane on the sensor contributes to a compactdesign.

High pressure stability can be realized by mounting the membrane on agas-permeable carrier.

High pressure resistance combined with low flow resistance to the gas tobe measured can be achieved by constructing the carrier of a porousmaterial.

Designing the membrane to be gas-permeable in both directionscontributes to a high degree of measurement dynamics.

Short response times are promoted by installing a pump on the outside ofthe housing.

It is conducive to sustained underwater use if the membrane hasantifouling properties.

The installation of a temperature stabilizer in the inner chamber of thehousing helps to further ensure highly accurate measuring results.

Further reduction of the response times can be achieved by installing atleast one pump in the inner chamber of the housing.

Specific embodiments of the invention are schematically illustrated inthe drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a schematic cross section through a measurement system.

FIG. 2 is a schematic drawing that illustrates the operating principle.

FIG. 3 is a more detailed schematic drawing of the measurement systemwith the associated electric components.

DETAILED DESCRIPTION OF THE INVENTION

In the embodiment shown in FIG. 1, the measurement system consists of ahousing 1, which has an inner chamber 2. A sensor 3 is installed in theinner chamber 2. A membrane 4 bounds part of the inner chamber 2 and issupported by the housing 1. The membrane can be designed as aconventional membrane or can be formed as a coating. In the illustratedembodiment, the membrane extends partly beyond a carrier 5. Thisprovides increased mechanical stability. The carrier 5 can consist ofany desired gas-permeable materials. Especially the use of a porousmaterial is contemplated.

The membrane 4 is gas-permeable in both directions, so that gas flow canoccur in both an inflow direction 6 and an outflow direction 7.

The sensor 3 can be designed, for example, for the detection ofhydrocarbons or other gases. For example, methane, butane, or propanecan be measured. However, it is also basically possible to use thesensor 3 to determine any other desired physical, chemical, orbiological parameters.

A thermocatalytic element 8 is also installed in the inner chamber 2next to the sensor 3. The thermocatalytic element 8 can be realized, forexample, as a thermocatalytic sensor. A thermocatalytic sensor usuallycarries out the combustion of a substance that is to be decomposed. Forexample, it is possible, with the addition of oxygen, to decomposemethane thermocatalytically into carbon dioxide and water.

FIG. 2 illustrates one use of the measurement system. In this case, gascirculation is provided within the housing 1, for example, by at leastone pump (not shown). Gas passing through the membrane 4 from anexternal medium 9, for example, water, is conveyed through a line 10 tothe sensor 3, through which it flows. The gas is then conveyed past athermocatalytic element 8 through a line 11 and passes back out throughthe membrane 4. In this connection, the fraction of gas of measurementinterest is reduced with the use of the thermocatalytic element 8 insuch a way that the emerging gas does not appreciably adulterate the gasentering in the inflow direction 6 with respect to the concentrations ofinterest.

Examples of sensors 3 that can be used are optical sensors orsemiconductor sensors. Membranes 4 are understood to include both actualmembranes and coatings with membrane-like properties.

Silicones or silicone-like substances can be used as materials formaking the membrane 4, but in principle it is also possible to use avariety of other materials. The membrane 4 typically has both thefunction of selectively supplying the gas to be measured to the sensor 3and the function of protecting the sensor 3 from penetration by water inthe case of underwater applications. It is also possible to use variantsof membranes that allow all gases contained in the water to passthrough. The carrier 5 has been found to be advantageous especially whenthe measurement system is used at great water depths, since it greatlyimproves the mechanical stability of the membrane 4. The design allowsapplications at depths of up to 6,000 meters.

With the use of the measurement system, it is possible to measure bothgases dissolved in the water and, for example, gases present in thewater in the form of gas bubbles or adsorbed gases. The measurementsystem can also be inserted in sediment or on the ocean floor formeasuring gases present there, for example, hydrocarbons. Besides theaforementioned measurement of hydrocarbons, such as methane, ethane,propane, and butane, other gases, for example, carbon dioxide orhydrogen sulfide, can also be measured by selecting suitable sensors 3.

There are basically many different areas of applications, for example,the following: leakage detection in offshore pipelines, measurements onsubmarine volcanoes, measurements on hydrothermal vents, measurement insewage treatment plants of dumps, methane outlets in tunnel shafts forroads, measurement of methane in bore holes, general measurements inoceanography, methane in tidelands, biogas plants, offshore safety ondrilling and pumping platforms, production of methane hydrates in thelaboratory, exploration of natural gas and petroleum deposits, detectionof groundwater emergence near coastlines, methane measurements in oceansand methane gas sources in channels (marine seeps).

FIG. 3 shows a more detailed design realization of the measurementsystem. Two sensors 3 are installed in the inner chamber 2 of thehousing. The first sensor 3 is designed as a semiconductor sensor fordetecting at least one gas. The second sensor 3 is designed as aninfrared sensor, especially in the NDIR wavelength range, for thedetection of at least one gas. A thermocatalytic sensor realized as apellistor is used as the thermocatalytic element 8. This sensor issuitable for the detection of hydrocarbons and, specifically, can carryout a combustion of hydrocarbons.

A pump 12 is installed on the outside of the housing 1. If the externalmedium 9 is water, the pump 12 is realized as a water pump. The pump 12produces flow of the water and thus of the gases dissolved in the waterin the direction of the membrane 4, thereby causing turbulence in thevicinity of the outer boundary of the membrane 4. This turbulence leadsto increased desorption of the gas by the membrane 4. The inner chamber2 of the housing is equipped with a pump 13 to promote gas circulationand thus further increase measuring effectiveness.

The measurement system has a power supply 14. To allow mobileapplications, the power supply 14 is realized, for example, as a batteryor secondary cell. In a typical embodiment, the sensor or sensors 3 arerealized as analog sensors, whose output signal is supplied to one ormore analog-to-digital converters 15, which convert the measuringsignals to digital signals that can be further processed. Theanalog-to-digital converter 15 can be connected, for example, with adata storage device 16 to document the performance of the measurementand/or to allow time-shifted data evaluation.

The measurement system is also equipped with a control unit 17, whichhas a memory 18, a monitoring unit 19 and an interface 20. The memory 18can be designed, for example, as a flash ROM. A mini-PC with one or moremicroprocessors and other electronic components can be used as themonitoring unit 19. The interface 20 serves especially for carrying outa data transmission, optionally, online or offline.

A temperature stabilizer 21 mounted in the inner chamber 2 of thehousing 1 contributes to further improvement of measurement quality. Inapplications involving moist conditions, the temperature stabilizer 21prevents especially the temperature from falling below the dew point. Inaddition, however, large temperature variations would have unfavorableeffects on measurement accuracy.

1. A device for acquiring measurement data for determining gases in liquid, which has a housing for use in water, an inner chamber of the housing, and a flat membrane that is supported by the housing and bounds part of the inner chamber of the housing, and in which at least one sensor for measuring gases in liquids is installed within the inner chamber of the housing, wherein the sensor includes a thermocatalytic element (8) for decomposing at least one gaseous hydrocarbon in the inner chamber (2) of the housing and where the inner chamber (2) of the housing is designed in a way that supports gas circulation, wherein a temperature stabilizer is arranged in the housing, the sensor being constructed so that decomposition of a hydrocarbon by the thermocatalytic element takes place in the inner chamber with improved measurement dynamics and reduced lag time, wherein the membrane is gas-permeable in both directions and has a backside mounted on a gas-permeable carrier so that the carrier mechanically reinforces the membrane so as to permit use of the membrane at depths of up to 6,000 meters, wherein a pump for generating continuous gas circulation is arranged in the inner chamber of the housing so that the gas circulation of measurement air is continuous between the membrane and the at least one sensor to provide a continuous equilibration of the same measurement air/medium and reduce reaction time.
 2. A device in accordance with claim 1, wherein the sensor (3) is designed as an optical sensor.
 3. A device in accordance with claim 1, wherein the sensor (3) is designed as a semiconductor sensor.
 4. A device in accordance with claim 1, wherein the membrane (4) is formed as a coating.
 5. A device in accordance with claim 1, wherein the carrier (5) is made of a porous material.
 6. A device in accordance with claim 1, wherein a pump is installed on the outside of the housing (1).
 7. A device in accordance with claim 1, wherein the membrane (4) has antifouling properties. 